Had a sort of Gentleman's Bestiary description just pop into my head. Here we go.

The BubbleBoy"Through either consumption or consummation, this monster takes in the DNA of its victims, storing it in the sack-like protrusion on its back. Through an as yet unexplained process, the stored DNA replicates thanks to continuous "feeding" and eventually results in the "birth" of a fully formed Bubbleboy. When the new Bubbleboy has been expended, the sack deflates. This process of procreation is entirely unique to the Zombie Hordes previously studied, and should be avoided at all costs."